The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
There is increasing interest in the use of energy harvesting apparatuses and methods for harvesting vibration energy experienced by various forms of mobile platforms, for example, spacecraft, aircraft, and automotive vehicles. Energy harvesting apparatuses and methods can be used to harvest vibration energy for the purpose of generating electrical signals to power various forms of sensors or actuators, or to control other electronic or electro-mechanical devices.
Previously developed vibration harvesting devices often make use of a cantilever beam. The cantilever beam is fixedly supported from a support structure at a first end, where the first structure experiences vibration energy. A second end of the cantilever beam is free to move in response to the vibration energy experienced by the beam. The vibration energy typically forms a force that is applied along an axis that is directed perpendicular to the longitudinal length of the beam at the outermost tip of the beam (i.e., in this example the second end of the beam), as indicated in FIG. 1. When such a perpendicularly directed force is applied to the beam, typically the stress and/or strain experienced by the beam is greatest at the root area of the beam (i.e., the area where the beam is secured to the support structure) when the beam flexes into the dashed position shown in FIG. 1. For example, if the beam comprises a piezoceramic material, the energy distribution within the piezoceramic material may look similar to what is disclosed in FIG. 2. FIG. 2 illustrates that the majority of the piezoceramic energy developed during flexing of the beam occurs at the root area of the beam. Thus, a majority of the length of the beam produces only a small amount of energy as the beam is deflected. This characteristic thus tends to limit the efficiency of the piezoceramic material of the beam in generating electrical energy during flexing movement of the beam.
The above shortcomings with cantilever beams apply with equal force to applications where the cantilever beam is being used to convert electrical energy into mechanical motion. With such systems, the inefficiency of the cantilever beam arrangement results in only a relatively small degree of bending of the cantilever beam, principally at its root, when the electrical signal is applied. Consequently, only a limited amount of mechanical motion is provided for a given magnitude of electrical signal. This drawback has limited the efficiency/effectiveness of cantilever beam systems in motor and fluid control applications.